Preparation of an interpenetrating bimetal metal–organic framework via metal metathesis used for promoting gas adsorption

Abstract

Metal–organic frameworks (MOFs), which allow precise control over their porous environment, have attracted extensive research attention in the field of gas adsorption. In this study, an interpenetrating bimetal Cr-based MOF (termed MIL-126(Cr/Sc)) with trigonal-prismatic M₃O (M = Cr/Sc, 61/39%) secondary building units has been synthesized using a metal metathesis method, and it retains the structure and porosity of the MIL-126(Sc) template and shows by far the highest thermal stability among the Cr-based tricyclic MOFs reported to date. Single component isotherm measurements have revealed that MIL-126(Cr/Sc) displays a higher CO₂, N₂O and C₂H₂ uptake under ambient conditions, and a larger gas uptake at low pressure when compared to pristine MIL-126(Sc). The results of our theoretical calculations indicated that the open Cr(III) site had a stronger interaction with gas molecules than an open Sc(III) site, thus promoting the gas capture capacity of MIL-126(Cr/Sc). These findings will facilitate further deliberate post-synthetic modifications of MOFs with open metal sites to promote their gas sorption capacity.